The present invention relates to vehicle braking systems. It finds particular application in conjunction with service braking systems and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
Heavy vehicles typically include hydraulic or air braking systems. During a service brake application, a suspended brake pedal is depressed in a forward direction from an initial position by an operator's foot. Upon release, a return spring may cause the brake pedal to over-travel rearward and momentarily “snap back” too far rear of the initial (neutral) position (before returning to rest at the initial position). Other conditions that may cause the brake pedal to over-travel are when the pedal is grabbed by an operator while getting into or cleaning the vehicle, when the operator's foot slips off the pedal or when the pedal gets hooked onto an operator's shoe. While the pedal is rearward of the initial position, a linkage malfunction may occur. For example, a brake (push) rod may become disengaged from an associated reaction pin of the master cylinder. If such a disengagement occurs, the pedal rod may drop below the reaction pin and result in loss of braking ability.
A loss of braking ability may also occur if a roller is used to apply force to the brake valve. In “slip foot” testing, if the brake pedal is allowed to “snap back” unrestricted past the initial position, a brake control arm (e.g., plunger) may fall out of a plunger guide of a brake component, thereby resulting in a loss of braking ability.
The issue of disengagement has become more complex with the introduction of adjustable brake pedals.
The present invention provides a new and improved apparatus and method.